The present invention relates to an apparatus for continuous pressure feeding of slurry for use in a liquefying plant or the like and more particularly an apparatus for continuous pressure feeding of slurry, in which even in the case that a sensor for detecting a position of a float is inoperative due to a turbulence from the outside, the operational sequence may be continued.
For instance, in U.S. Pat. No. 3,556,682, there is disclosed an apparatus which comprises a plurality of supply chambers or vessels arranged in parallel, a low pressure pump for filling the supply chambers with slurry consisting of water and solid material and a high pressure pump for driving liquid for discharging the slurry from the supply chambers to a transmitting pipe, and in which a position of a float floating on the interface between the slurry and the driving liquid is detected by an external sensor, and in accordance with the detecting signal, valves interposed in inlet and outlet pipes for the driving liquid and in inlet and outlet pipes for the slurry are selectively opened or closed thereby transferring the slurry by utilizing the pressure of the driving liquid.
However, in the case where the sensors disposed at upper and lower limit positions outside of the supply chambers are inoperative due to an external turbulence (e.g. noises caused by lightning), the operational sequence becomes abnormal or discontinued so that the apparatus as a whole is at a standstill and finally, a continuous operation of the entire plant is no longer possible.
Unless the sensors detect the positions of the float, the following problems are raised. As a first problem, in the case where the upper limit sensor is inoperative resulting in failure in detecting the float position, the float is not stopped at the position of the sensor and it reaches the upper portion of the supply chamber. At the same time, the driving liquid discharge valve is not closed, so that the slurry supplied from the slurry pump passes through the discharge valve and is mixed into the driving liquid tank. The mixed slurry is drawn by the high pressure pump. As a result, the high pressure pump is subjected to a remarkable damage. Also, the operational sequence is discontinued so that the entire apparatus is stopped.
As another problem, in the case where the lower limit sensor is inoperative resulting in failure in detecting the float position, the float is not stopped at the lower limit sensor and it reaches the lower portion of the supply chamber. At the same time, since the driving liquid supply valve is not closed, the driving liquid supplied from the high pressure pump passes a check valve on the transferring pipe, so that the transferring performance of the slurry is lowered. Also, the operational sequence is discontinued so that the entire apparatus is stopped.